The present invention relates generally to rotational control apparatus, particularly to provisions supported directly by the shaft for providing fluid pressure to a rotation control apparatus portion rotatable with respect to the shaft, and specifically to dual-rotary union, rotational isolation adapters.
Problems exist particularly in connection with fluid actuated rotational control apparatus. In such rotational control apparatus, a source of fluid pressure is in fluid communication with a part of the rotational control apparatus such as a piston which is to be actuated. If such part is rotating and the source of fluid pressure is stationary, as it generally is, problems exist in regard to providing such fluid communication.
These problems particularly arise in clutches or the like, since brakes generally have a portion which is stationary with respect to the source of fluid pressure or external housing. In the case of brakes, fluid communication and actuation may often be made with respect to such stationary portion. Clutches, in contradistinction, are generally composed of at least two portions, with one portion connected to the shaft either directly or through intervening elements, and another portion which is rotatably mounted with respect to the shaft and which interacts with the first portion. Thus, suitable provisions such as rotary unions must be provided for allowing fluid communication between a stationary source of fluid pressure and one rotating portion of the clutch.
If the portion of the rotational control apparatus desired to be actuated rotates with the shaft, the rotary union could be directly or indirectly connected to the shaft. For example, U.S. Pat. No. 4,408,685 assigned to Horton Industries, Inc. discloses structure of this type to solve this problem.
On the other hand, if the portion of the rotational control apparatus desired to be actuated is rotatably mounted with respect to the shaft, the rotary union could be directly or indirectly connected to the portion which is rotatably mounted with respect to the shaft. Often this portion is in the form of a housing and the rotary union is connected to an end cap for this housing. An example of such an end cap approach is shown in U.S. Pat. No. 4,425,993 also assigned to Horton Industries, Inc. When an end cap approach is used, however, and especially if the apparatus has a large radius, the end cap approach can present significant design problems. The end cap adds weight, adds inertia, and increases costs. The end cap requires careful machining to allow for balance. The end cap provides centrifugal problems because of the large amount of mass radially spaced from the shaft upon which it is generally centered for rotation.
In situations where it is wished to provide fluid pressure from a stationary source to a rotational control apparatus such as a clutch, in particular, where the portion to which fluid pressure is desired is rotatably mounted with respect to the shaft, it has been discovered that no solution was known where the rotary union is mounted directly to the shaft but rotatably isolated from the shaft to avoid the problems encountered by end cap type approaches.